Construction and Maintenance of the Building - Case Study Example

Construction and Maintenance of Building Submitted by……………………………………….. Introduction A new project has been proposed to build a new college building for Barking and Dagenham College. It shall be built on the site ground. It has been specified that twenty-four learning spaces are to be constructed should include: a testing lab, a conference centre, a basement and Office space, a staff room, first aid room, tutorial room, an administration office and management office. The whole building will be accommodated on two floors with additional storage in a basement. The client has requested a flat roof suitable for future further extension and development and green space to be provided for conversion into a small garden. In addition, the primary source of energy for the building will be generated from a Combined Heat and Power (CHP) unit. Combined power and heat integrates the production of usable heat and power (electricity), in one single, cost effective and highly efficient process. The CHP system is sustainable, clean and renewable. CHP generates electricity while also capturing usable heat that is produced in this process its efficiency is greatly increased. This is unusual contrasts with conventional ways of generating electricity where heat is simply wasted and in the process impacting negatively on efficiency. In today’s coal and gas-fired power stations, up to two-thirds of the entire energy consumed get lost in such a way, frequently witnessed as a cloud of smoke rising from the cooling turrets, the process is very environmentally unfriendly. This will be a very eco-friendly aspect of construction as it is very efficient in its purpose and design. Main Building Size Measuring 25m X 15m Engineering workshop Measuring 7m X 5m Sub-structure or Foundation- is the lower section of the building, located below the ground level and the damp proof course. A foundation is part of the structure that is in direct contact with the ground to which the loads are equally transmitted to the supporting surrounding soil. Shrinkable soils are those types whose contents are made up of more than 35% have a modified plasticity index greater or equal to 10% and of fine particles. The fine soil particles are having nominal diameters of 60 µm. Plastic index of a given soil is its measure of the change in volume potential that is determined by Atterberg Limits test. Soil particles whose nominal diameters after the test are greater than 425 µm are eliminated through sieving in advance. Particles with diameters smaller than 425 µm are promptly reported for Atterberg Limits test. The Plasticity index of the soil multiplied by the real percentage of particles with contents less than 425 µm is the measure of its Modified plasticity index. The relationship of the indexes is as shown below: Table 1: Volume potential change Modified Plastic Index Volume change potential 10% to less than 20% low 20% to less than 40% Medium 40% and above High For pure clay soil and other types of soil with 100% particle size less than 425 µm, the result yields the same. Nonetheless, for soil with mixed particle strength, modified plastic index use may give a more economic design. The potential change in volume for a particular soil should be properly established from the site from the local knowledge of the area geology. Enough samples should be investigated to provide confidence that the results of tests performed are representative of the soil potential change in volume for that specific site. When in doubt a higher volume is used. In scenarios when the volume change is not known, we assume a higher change volume potential. The surrounding soil can affect the substructure due to its properties and possible contaminants. The soil will originally have to be tested so that the design can be altered to suit. Soils can be tested through pre-construction site surveys/walk over surveys – the two most commonly used forms for classification are trials pits and bore holes among others. A trial pit is an excavation in the ground which helps and allows us to investigate or sample the structure and composition of the subsurface, this is usually dug during a site investigation, analysis or a soil survey. Usually, the trial pits are burrowed before the construction so as to ascertain the water table and geology of that site. These trial pits are normally between one and four meters deep and are dug either by hand or using a mechanical digger. Building and construction regulations state that any trail pits that are deeper than 1.2meters should be secured against structural collapse, especially if people are working in them. The idea of boring is to gain an understanding of what the ground is like in order to be able to determine what type of foundations are required for the proposed project. The plant used to carry out boring is called a Hand Auger, it is suitable for sand, silt and soft clay, however, when in contact with stiff clays, hard materials and gravels, the Hand Auger isn’t as easy to drill through and remove. The hand auger comprises of extendable steel rods that are simply rotated by a handle. A wide variety of different steel augers (heads) may be embedded at the bottom of the engineers` drill rods after which the augers get rotated in the ground up to when they are filled. They are then lifted out of the borehole to be emptied. Form every excavation process a different auger can be used for each soil type. Hand auguring can be done either by using a heavy tripod structure and a winch or with lighter materials depending on the toughness of the soil. The given site grounds as attached state within the given borehole records that there is a trace of asbestos in the ground. Asbestos fibrous silicate is always a highly heat-resistant mineral which has been woven into fabrics and is used in linings and fire-resistant and insulating materials. It is commonly found in buildings and structures build in the 1950’s to the late 1990’s. It is found mainly in ceiling tiles, pipe insulation, boilers, sprayed coatings as well as garage roof tiles. Asbestos isn’t a major concern to have in a building as long as it isn’t disturbed. Inhaling loose fibres of asbestos is known to be the cause of serious and ever fatal lung diseases. You can overcome the contamination of asbestos two ways, concealing the contaminated area with concrete so that it can’t be disturbed or contacting an asbestos specialist for the correct and regulates disposal of the potentially harmful product. Finding asbestos on your site can cause great difficulties for the project financially and well as a risk of failing to meet the original deadline. Tests are to be carried out before the decision of the foundation type is chosen examples of these are the previously mentioned boreholes and trial pits. As listed in the 6th edition of the Cuddly construction handbook there are several options that can be chosen from if the investigations reveal that the subsoil surrounding the substructure is naturally poor then choices explained below may be considered. a) Not to build- to look for a better site to build on. This can cause great delays to the finished project reaching completion as well as possible financial impacts as a new site could come at a greater cost. b) Remove and replace- the poor ground can be excavated, removed and replaced. This is costly to carry out, and the soil might not be as stable as the original due to the lack of natural compression of the soil among other factors. c) Surcharging- this involves preloading the poor ground with a surcharge of aggregate or similar material to speed up settlement. This will improve the soil bearing capacity. This is a very uneconomic method due to the time delay before the actual construction commencement creating an impact to the project varying from a few weeks to a few years. d) Vibration- this is a soil strengthening method through vibration. It works by vibrating a granular soil into compacted stone columns either by using the natural coarse granular soil or by replacement. e) Dynamic Compaction – this method of soil improvement which consists of dropping a heavy weight through a considerable vertical distance to compact the soil and improving its bearing capacity. This is especially suitable for granular soils. f) Jet Grouting- This method of consolidating ground can be used in all types of subsoil and consists of lowering a monitor probe into a 150mm diameter preloaded guide hole, The probe has two jets – the upper of which blasts water, concentrated by compressed air to force any loose material up the guild to ground level and the lower jet fills the void with a cement slurry which sets into a solid mass. General Principles of water proofing Water has a significant impact on the various elements of the structure and the architectural design. Prompt consideration and diagnosis of the water content in a site is very useful in preventing instances where design cost rises as a result of structural redesign or compromising waterproofing relative to achieving the environmental standards. The amount of water in a site will determine the design and the specialist to be engaged in the site. Suitable and correct design again is the fast step in attaining the desired outcome. The site investigation process guides the design. If no site investigation process is done, sensible doubt as to the groundwater situations, full height pressure below the ground substructure is assumed at some point. Water resisting design The standard behind this is to contemplate and design for pressures that the substructure must resist. This is based on the risk assessments and the site investigation results. What is also considered is how the ground water can be influenced by the design. Critically the ability of the substructure to provide resistance to any water penetration has a bearing on all other methods of waterproofing. The extent of water barred by elements of the concrete is determined by the construction and design nature (Levy, 2001). While it’s true that concrete is impermeable, the level to which water is barred from penetrating into the structure is dependent on the detailing and crack sizes of the services penetration and construction joints. Design Approach The superstructure that exist between the underlying soil and the interfacing element is the foundation. Loads subjected to the foundation to the underlying soil may cause soil shear failure or damage superstructure settlement. The design approach below is used to establish the correct optimum foundation solution. a) Foundation loads that are to be supported are determined, and this normally include: structure layout, total limits and differential settlement, scour, seismic performance alongside other time constraints. b) The subsurface laboratory testing data and exploration are performed considering loads to be transferred to and supported by, the rock/or soil. c) Critical soil section and final soil profile are prepared. Suitable and unsuitable soil layers are determined for pile foundation and spread footing. Ground improvement methods may be employed to help modify layers unsuitable into suitable support layers. d) All alternative designs are considered for shallow foundation requirements without ground improvements, shallow foundation requirements with ground improvements and deep foundation requirements. e) Feasible alternative designs for foundation including the associated substructure are estimated in cost. f) The last stage is the selection of the optimum foundation alternative. Note that the most cost g) An effective alternative is recommended for selection. Table 1: Typical Foundation Types and Uses Foundation Type Application Applicable Soil Condition Non-suitable Soil Conditions Spread/wall footings Columns, walls Adequate bearing capacity for loads Applicable in areas where bearing layer is within 10 feet of the ground surface. Applicable where foundations are reinforced on soils subject to liquefaction and bearing layer situated below the water table. Pile foundations Grouped to transmit heavy columns. Resist lateral loads. Near surface and poor surface soils. Soil appropriate for load support 15 to 150 ft. off the ground. Establish settlement of ground piling. Hard stratum require shallow depth. Site with heavy pile vibrations adversely impact adjacent facilities. Mat foundations Similar to wall footing and spread. Very large and heavy column loads Soil value bearing is less than that of spread footings. More than half area covered by footings. Is able to check settlement. Similar as for spread footings Drilled shafts Heavy and large loads than for piles Near surface and poor surface soils. Soil appropriate for load support 25 to 300 ft. off the ground. Establish settlement of ground piling. Deep loose and soft clay, granular, water bearing soils. Difficult to stabilize and caving formations. Conditions that are Artesian. Table 2: Determination of D/H Value Spread footing is the feasible option for foundation support for any further selection. They are more effective in terms of cost as compared drilled shafts and piles. Next option in the selection process includes spread footings with ground water improvement option. Table 3: Foundation Designs It’s further noted that deep foundations must not be considered for any foundation and substructure process because they are subsurface condition which are very costly and difficult to install. Shallow foundation evaluation includes; a) Depth dimensioning of shallow footing based on allowable bearing capacity. b) Time rate and magnitude of settlement under loads. c) Comprehensive cost analysis that canvasses overall substructure costs, need for cofferdams, foundation seals and dewatering, construction time, claims potential and construction risks, all which have significant influence on the final selection type. Bibliography Levy, S. M. (2001). Construction site work, site utilities, and substructures databook: [excavation and soils ; piping specifications ; concrete, masonry ; piles, caissons, rock and soil anchors ; equipment selection]. New York, NY: McGraw-Hill. Read More